In a linear guidance portion of a work table of a machine tool or of various conveying devices, there is widely used a rolling guidance device in which a movement block with a movable body such as a table mounted thereon moves continuously along a raceway rail. In a rolling guidance device of this type, the movement block is assembled to the raceway rail through the intermediation of a large number of balls, and the balls roll while bearing a load between the movement block and the raceway rail, whereby it is possible for the movable member mounted to the movement block to make a smooth movement along the raceway rail while involving little resistance. Further, the movement block is provided with an endless circulation path for the balls, and the balls are allowed to circulate in this endless circulation path, whereby it is possible for the movement block to move continuously along the raceway rail.
Conventional examples of the mainly used movement blocks include a block main body made of metal and an end cap made of synthetic resin, which is coupled to each of both ends of the block main body. In the block main body, there is formed a load rolling groove in which the balls roll while bearing a load between the block main body and a ball rolling groove of a raceway rail, and is provided with a non-load ball path grooved in parallel with the load rolling groove. In order to suppress the temporal friction with respect to rolling of the balls, the block main body is made of steel capable of being quenched, for example. Further, the end cap is provided with a direction changing path which is formed through injection molding of a synthetic resin so as to achieve a complicated configuration. In this context, a pair of end caps are accurately fixed with respect to both the front and rear end surfaces of the block main body, whereby the end of the load rolling path and the end of the non-load ball path are coupled through an intermediation of the direction changing path. In this way, the movement block provided with the endless circulation path for the balls is completed.
However, there is a problem in that the conventional movement block as described above requires much time and effort in working and assembly thereof, which leads to an increase in manufacturing cost thereof.
Meanwhile, WO2006-022242 A1 discloses a linear guidance device in which a structure of the movement block is dramatically simplified. In the linear guidance device, the endless circulation path for the balls is formed as a track groove with respect to the movement block made of metal, the movement block being formed of a single metal piece. The track groove includes the load straight-line groove in which the balls roll while bearing a load between the load straight-line groove and the ball rolling groove of the raceway rail, the pair of ball deflection grooves which are provided at both the ends of the load straight-line groove so as to change the rolling direction of the balls having rolled in the load straight-line groove such that the balls are allowed to leave the ball rolling groove of the raceway rail, and the non-load straight-line groove for transferring the balls in a non-load state from one ball deflection groove to the other ball deflection groove. The track groove is formed at the position of being faced with the raceway rail of the movement block, whereby the balls rolling in a non-load state in the ball deflection groove and the non-load straight-line groove are prevented from leaving the track groove.
Further, WO 2006-064734 A1 discloses a similar linear guidance device. In the linear guidance device, the track groove is formed in the ball circulation plate which is provided separately from the movement block. The ball circulation plate is engaged with the movement block, whereby the track groove can be positioned while being faced with the raceway rail.
The track groove can be formed continuously with the movement block or the ball circulation plate through cutting with use of an end mill. This configuration contributes to reduction in manufacturing cost when compared with that of the conventional linear guidance device which requires the end caps.                Patent Document 1: WO 2006-022242 A1        Patent Document 2: WO 2006-064734 A1        